Oil-cooled transformer



Nov. 17, 192s.V 1,562,428

R. V. BINGAY OIL COOLED TRANSFORMER Filed Nov. 8, 1920 54 Sme/nio@ /af a55 MJOIZS /7 Patented Nov. 17, 1925.

vmuren ROBERT V. BINGAY, OF PITTSBURGH, PENNSYLVANIA, ASSIGl'NOE' TOPITTSBURGH TRANSFORIVIER COMPANY. A CORPORATIONDF PENNSYLVANIA.

GIL-COOLED TRANSFORMER.

Application led November 8, 1920. Serial No. l122,465i

`To all whom it may concern.'

State of Pennsylvania, have invented cer` tain new and usefulImprovements in Oil- Cooled Transformers, of which the following is aspecification.

This inventionrelates to transformers and particularly to transformerscooled by a circula-ting liquid `such as oil.l Such transformers areusually placed in a tank pontaining the cooling oilwhich is heated bythe transformer and transfers this heat to the outer portion of thetank; The cooling oil is also an insulator and in order to preserve theoil and maintain its insulating properties it has been found desirableto protect it against contact with the outer air.

The object of this invention is to provide a transformer containingmeans that `will retain the oil out of contact with the surroundingatmosphere and at thesametime.

permit of expansion and/contraction of the oil duetoltemperatur'changes.

In the embodiments of the invent-ion shown in the drawings,

Fig. l is an elevational view of a transformer tank and expansion tankin connection therewith,

Fig. 2 is a similar view of a modified form, and

Fig. 3 is a similar diagrammatic -view illustrating a system adapted fora plurality of tanks.

In the embodiment of the invention shown in Fig. l a transformer tank Kon a. base B contains the transformer and cooling oil O. The tank K isfilled with the oil O up'to the under surface of the cover C to giveextended cooling contact and to restrict the area of Contact 'of oil andair, the wholev tank being oil and air tight. To permit ex# pansion ofthe oil when heated expan' sion tank E is provided for instance standingon thev base B beside the tank K and connected thereto by pipe P havingthe three-way cock 9 to close the pipe in both directions or open aconnection between the tanks E and K or to close thev connection to tankK and open the bottom of tank E to discharge the oil therefrom. The pipeP and tank E are oil and air tight and when the transformer is connectedin lcircuit it heats the oil O which expands an amount de endent ingeneral upon the temperature rlse of the oil, compressing the gas or airin the tank E and raising its pressure correspondingly.Upondisconnection ofthe transformer and coolin of the oil the gaspressure in tank E will orcc2 the oil back into tank Kto maintain thelatter always full, and it isto be noted that at no time is there anythe outer air. I

An overheating of the oil O and resultant excessive rise inv pressuremay be taken care of by the safety blowolf W of the tank K or a safetyvalve V may be provided on tank E to relieve the pressure. The pressuregage S may also be provided in connection with vthe tank E and an oillevel gage L and air introducing means A comprising for instance acylinder D containing a drying agent' suchas calciuml chloride andhaving a pump or pump connection at its outer end to force in air.

Under normal conditions of operation the apparatus of this inventionwill retain the transformer oil sealed against escape and againstcontact with the outer atmosphere so that the liquid cooling system-ishermetically sealed and a circular oat member R may be provided to iioaton the surface of the oil in tank E to further restrict communicationwith the contact with the air or gas contained in the system. The tank Kwhen cool may be just completely filled for instance to a level l() oran overflow of the oil through pipe P into ltank E may be permitted toestablish its own level such as l1 in the tank E or this level may bepumped to any desired point such as l2 and even back up in pipe P bypressur'e through the pump connection A.

If with cool oil the oil pressure at the top of tank K is substantiallyatmospheric then the gaslpressurc in tank E will be atmos# pheric forlevel l() of the oil or for level 11 or 12 it will be thatA ofthecorresponding lUO lcvelin tank K, for instance a few pounds vin' tank' Ewill be transferred by pipe P to the oil in tank K and when thetransformer is in operation the oil O will be under pressure.`

The tank E instead of resting on the transformer base may, whereconvenient, be mounted in elevated position for instance on top of thetransformer cover C as shown 1n Fig. 2 in connection with the tank E',pipe I and cock 20, and its operation here will be substantially similarto that in Fig. l, the gas pressure and its changes being, however, lessin this elevated position for a given expansion of the oil so that thepressure variations on the oil in the tank K will be reduced for a givensize of expansion tank. These variations would be still further reducedby a higher elevation of the expansion tank and the reduction of thepressure in the expansion tank below atmospheric for instance to a valuesufficient to give at- 'mospheric pressure at the top of tank K.

Where there are a numbei of transformers as indicated in diagram in-Fig. 3, the oil supply of all of these transformers may be connected toa single expansion tank preferably placed at an elevated position andacting as a common receptacle for the expansion from all of thetransformers. 'This system has the advantage not only of saving aseparate tank for each transformer but also of giving a more nearlyconstant, average pressure in all of the tanks.- The tank E of thissystem will have its pipes P1, P2', P3, etc., provided with controlcocks 31, 32, 33, etc., so that any transformer may be disconnectedwithout affecting the others.

The connection of pipe P to the trans- 'forrner tank K is preferablymade at an extreme top point so that a-lr or gas in the tank will becarried over into the expansion tank E and will not remain trapped inthe main tank above the level of the pipe opening. Wrhile in theforegoing illustrations of the operation of the expansion system the oilpressure at the top of the transformer tank when coolhas been assumed assubstantially atmospheric it may in the tank of this. invention be belowatmospheric so'that the subsequent pressure on the hot oil at the top ofthe tank will be more nearly at'- mospheric. i

In the expansion system of this invention the oil is kept out of contactwith the atmosphere so that moisture is excluded and oxygenation of theoil is prevented and the oil is preserved indefinitely. Under normaloperation the system requires no attention and after. severe overheatingand over pressure it is only necessary with the tank of Fig. l to pumpin air or gas to replace that exhausted -by the safety valve. With theexpansion tank in raised positionthe air pump A may be replaced byautomatic vmeans operating to admit air when the pressure drops belowthe atmospheric. The expansion apparatus is simple and inexpensive andeasily adaptable to differing conditions of transformer installationsand while the invention has been described in connection confinedthereto but is intended to cover such modifications thereof as fallwithin the scope of the appended claims.

I claim:

1. In an expansion system for air cooled transformers the combinationwith a main transformer tank, of a non-expansible tank receiving theoverflow from said main tank and having a rigid closed top for trappingandvholding a gas above the surface of said overflow and preventingoutside air from havingaccess to the surface of the overflow during theexpansion of oil in said main tank. A

2. In an expansion system for air cooled transformers the combinationwith a plurality of main transformer tanks, of a single non-'expansibletank receiving the overflow from all of said main tanks and having arigid closed top for trapping and holding a gas above the surface ofsaid overflow and.

preventing outside' air from having access to the surface of theoverflow during the' expansion of oil in said main tanks.

3. In an expansion system for transformer tanks the'coinbination with amain tank, of an auxiliary nonexpansible expansion tank connectedtherewith and adapted to lower the pressure in the main tank to belowatmospheric when cool and permit it to rise above atmospheric during theheating of the oil in the main tank. h

4. In an expansion system for air cooled transformers the combinationwith a main transformer tank, of a non-expansible tank receiving theoverflow from said main tank and having a rigid closed top for trappingand holding a gas above the surface of said overflow and preventingoutside air from having access to the surface of the overflow during theexpansion of oil in said main tank, and means for exhausting gas fromsaid expansion tank when the gas pressure therein exceeds apredetermined amount.

5. In an expansion system for air cooled transformers the combinationwith a main transformer tank, of a non-expansible tank receiving theoverflow from said main tank and having a rigid closed top for trappingand holding a gas above the surface of said overflow and preventingOutside air from having access to the surface of the overflow during the.expansion of oil in said main tank, and means for introducing'air into,

said expansion tank. y

6. In an expansion system for air cooled transformers the combinationwith a main transformer tank, of a non-expansible tank receiving theoverflow from said main tank and having a rigid closed top for trappingand holding a gas above the surface of said overflow and preventingoutside air from havingv access to the surface of the overflow duringthe expansion of oil in said main tank,iand a member oating on thesurface of the overfiow in said expansion tank' and lmain tank andpreventing the outside air from having access to the surface of the oil,the oil and gas being hermetically sealed against the outside atmosphereduring normal operation.

8. In an expansion system for transformers the combination with amaintransformer tank, a rigid non-expansble auxiliary tank connectedthereto com letely closed for holding a gas compressedV `y the expansionof oil in the main tank and preventing the outside air from havingaccess to the surface of the'oil, the oiland gas being hermeticallysealed against the outside atmosphere during normal operation.

9. In an expansion system for transformers the combination Witha maintransformer tank, of an auxiliary tank connected thereto completelyclosed for holding a gasv compressed by the expansion of oil in the maintank and preventing the outside air from having access to the surface ofthe oil, the oil and gas being hermetically sealed against the outsideatmosphere durlng normal operation, and means permitting v"the escape ofgas above a predetermined pressure.

10. In an expansion system for transformers the combination with a' maintransformer tank, of an auxiliary tank connected' thereto completelyclosed for holding a gas compressed by the expansion of oil in the maintank and preventing the outside air from having access to the surface ofthe oil, the oil and gas being hermetically sealed against the outsideatmosphere during normal operation, means permitting the escape of gasabove a predetermined pressure, and means permitting the admission ofgas..

' ROBERT V. BINGAY.

